1. Field of the Invention
This invention relates to a punching system used in combination with an image formation system such as an electrophotographic copier or a printer for automatically making holes in a sheet material of recording paper, etc., to or on which an image is copied or recorded.
2. Description of the Related Art
Hitherto, punching systems used in combination with an image formation system such as an electrophotographic copier or a printer have already been proposed as disclosed in Japanese Patent Laid-Open No. Hei 3-92299, Hei 5-162919, etc., for example. An image formation system according to Japanese Patent Laid-Open No. Hei 3-92299 has a punching mechanism comprising a plurality of punches (also known as "punching edges") movable with respect to a paper transport passage, the punches being placed side by side in a predetermined spacing in a width direction of recording paper, characterized by paper center detection means for detecting the width direction center of paper based on detection information of a width direction end position of paper in the proximity of a punching section of the punching mechanism and alignment means for substantially matching the width direction center of paper with the arrangement center of the punches edges before punching.
The punching system for once stopping and punching recording paper discharged from an external system in the transport process according to Japanese Patent Laid-Open No. Hei 5-162919 comprises a punching means driving force transmission mechanism and a rotation claw stopper driving force transmission mechanism coupled to an output shaft of a single motor, a first one-way clutch for actuating the punching means driving force transmission mechanism when the output shaft forward rotates, a second one-way clutch for actuating the rotation claw stopper driving force transmission mechanism when the output shaft reversely rotates, punching means being actuated when the punching means driving force transmission mechanism is actuated for punching holes in recording paper on a transport passage, a rotation claw stopper being actuated when the rotation claw stopper driving force transmission mechanism is actuated for rotating between a recording paper stopping position and saving position, a driven discharge roller being loosely engaged on the same axis as the rotation claw stopper on a stopper shaft for pivotally supporting the rotation claw stopper, a driving discharge roller being coupled to the rotation claw stopper driving force transmission mechanism for driving and coming in contact with the driven discharge roller on an outer peripheral surface for rotating the driven discharge roller in conjunction, a clutch being placed between a driving shaft for pivotally supporting the driving discharge roller and the stopper shaft for turning on and off transmission of a driving force from the driving shaft to the stopper shaft, clutch actuation means for turning on and off the clutch, and a control section for controlling the motor and the clutch actuation means.
However, the prior arts involve the following problems: In Japanese Patent Laid-Open Nos. Hei 3-92299 and Hei 5-162919, the punching mechanism and the punch unit are moved in a direction perpendicular to the recording paper transport direction by, the alignment means, etc., in response to the width direction size of transported recording paper, whereby holes can always be punched in the substantial center portions of recording paper sheets different in width direction size. However, the paper center detection means for detecting the width direction center of paper based on detection information of a width direction end position of paper in the proximity of the punching section of the punching mechanism and the alignment means for substantially matching the width direction center of paper with the arrangement center of the punches before punching are operatively associated with each other. Thus, for recording paper which need not be punched, the paper center detection means may also detect the width direction center of paper based on detection information of the width direction end position of paper and move the punching mechanism so as to match the width direction center of paper with the arrangement center of the punches before punching; it is feared that electric power of the image formation system may be wasted or that starting the image formation operation may be delayed by the time required for moving the punching mechanism.
The punching mechanism of the punching system basically inserts recording paper between the punches and dies for receiving the punches and inserts the punches into the dies, thereby punching holes in predetermined positions of the recording paper. When the punching mechanism of the punching system is moved in response to the width direction size of the recording paper, if the punching section containing the punches and the die section are moved separately, it is feared that they may be placed out of position and the punches may come in contact with the dies, breaking the punches. Thus, the punching section and die section are mechanically coupled to each other at both end positions of the width direction where transport of recording paper is not disturbed and are moved in one piece.
By the way, in the punching system, if recording paper of a long width direction size which need not be punched is transported after recording paper of a short width direction size is punched, the end of the recording paper of a long width direction size is caught in the coupling part of the punch and die sections, causing a paper jam to occur. To circumvent this problem, if the coupling part of the punch and die sections is widened to a position where the coupling part is not caught in the recording paper of a long width direction size, the punching system is upsized, causing a new problem.
The punching system comprises the punching mechanism moved in response to the width direction size of recording paper. In an image formation system such as a copier to which the punching system is attached, sheets of recording paper varying in width direction position may be transported and punch positions vary from one sheet to another because of the variations in the width direction positions of recording paper. Thus, as described above, the punching system according to Japanese Patent Laid-Open No. Hei 3-92299 detects the width direction center of paper based on detection information of the width direction end position of paper by the paper center detection means and moves the punching mechanism by the alignment means so as to substantially match the width direction center of paper with the arrangement center of the punches before punching, thereby lessening the variations in the punch positions. However, the punching system according to Japanese Patent Laid-Open No. Hei 3-92299 uses a plurality of light emitting parts and light receiving parts placed facing each other for each of sheets different in width direction size as the detection means for detecting the width direction end position of paper, thus the detection means configuration becomes complicated and expensive, resulting in an increase in cost. Since the detection means for detecting the width direction end position of paper has the light emitting parts placed in physically discontinuous relation, the paper end positions that can be detected by the detection means are determined by the positional relationship among the light emitting parts and the paper end cannot be detected for the size between the adjacent light emitting parts or if the paper end can be detected, the detection precision lowers and a hole cannot accurately be punched in the center position of recording paper. Further, the punching system does not take any steps for a sheet skewed with respect to the recording paper transport direction and also involves a problem of worsening the punch position accuracy because of the skewed sheet.